Asdic "only"

[John Pancoast]

Originally Posted by Randomizer

Looking at some of the primary sources I suspect that active and passive searches were the norm.

Here US Fleet Anti-Submarine Instructions differentiates between search patterns and active-sonar search patterns (Echo Searches) so presumably passive listening with hydrophones were an option if conditions were suitable.

Buried in this tome is warnings about interference between escorts depending on the frequency of the active sonar (ASDIC) but not too much specific data. I suspect that these issues would have been addressed at the Operator/ASW Officer level and so not part of the Big Picture covered by this document. I had not considered this but it makes sense that coordination and control would be required to keep escorts from jamming each other.

Here Arctic Convoy Instructions there is a throw away entry regarding horrible acoustic conditions in the Arctic using ASDIC and the context suggests active rather than passive detection means. I think that it was Milner, in his book about U-Boats Against Canada, commented on the inability of ASDIC to find U-Boats in the Gulf of St Lawrence for a variety of reasons including fresh-water eddies bottom conditions and irregular thermal zones.

Food for thought though as these days active sensors can bring all sorts of nasty countermeasures but in WW2 it seems that the rules were "Ping all you want".

-C

Yes everything I've found states that asdic was constantly banging away 24/7 with fixed search patterns. I.e., x degrees arc port/starboard of the bowline with x degrees between each movement of the device.